Anti-shock cushioning products having various shapes are used in sports and a variety of safety fields. In order to recently cope with the increasing demand for wearability, bendability and breathability of cushioning products, the designs of materials and structures thereof are variously changed. In the production of cushioning products, cross-linked foams resulting from a series of chemical pressurizing, cross-linking and foaming are receiving more and more attention from the related manufacturers with regard to their material use. Methods of manufacturing a variety of personnel protection products using such cross-linked foams are variously proposed, and examples thereof include Korean Unexamined Patent Application Publication No. 2001-0017382, U.S. Pat. No. 6,743,325, and US Publication No. 2008-0113143.
Specifically, Korean Unexamined Patent Application Publication No. 2001-0017382 discloses a method of manufacturing a shin guard, by sequentially stacking fabric, an EVA cross-linked foam, and non-woven fabric, adhering them using an adhesive, and pressing them to form a molded body having a predetermined shape, which is then formed to have a variety of irregular shapes, and U.S. Pat. No. 6,743,325 discloses a method of manufacturing a guard in such a manner that closed cell polyethylene foam is attached at a predetermined size and interval to the upper surface of resiliently stretchable knitted fabric using a rolling cutter acting as a cutting knife and a jig by means of a heat-resistant hot-melt adhesive.
US Publication No. 2008-0113143 discloses an attachment method comprising subjecting two kinds of cross-linked foams having different properties to flame lamination at 370° C. or higher thus preparing a cross-linked foam having composite properties, which is then attached to the upper surface of resiliently 2- or 4-way stretchable knitted fabric using a rolling cutter acting as a cutting knife and a jig and a heat-resistant hot-melt adhesive under conditions of predetermined shape, size, and interval of the cross-linked foam being maintained.
Such conventional techniques are common in that the cross-linked foam in a single sheet shape having a predetermined size or in a sheet roll shape having a predetermined thickness is prepared, and then subjected to a series of subsequent processes, thus producing a variety of cushioning products such as cushioning pads, etc. However, in the case where the cushioning product is manufactured from the cross-linked foam in a sheet shape or a sheet roll shape, many limitations are imposed on the structures or numbers of the products because of use of a plurality of foams having an arbitrary shape obtained by cutting the foam in a planar sheet shape or a sheet roll shape using any cutting means.
Also, when these foams are used by being attached to fabric or being embedded in fabric, they cannot appropriately correspond to a variety of bending areas (or a variety of operations) of the human body. Even in the case where they are applied to specific products having a three-dimensional shape to form inherent bending at a specific portion, many problems must be overcome to thoroughly solve the above problem. Thus, the conventional techniques are limited in terms of stretchability, bendability and curved fitting to a target as composite characteristics required of cushioning products, and may also obstruct the flexible activity of the human body, and thus there are needs for fundamental alternatives therefor.
According to conventional methods proposed to improve bending flexibility and air permeability of products to which the cross-linked foams in a sheet or sheet roll shape are individually cut and attached, a plurality of individual cross-linked foams separated using a cutting process may be attached to one surface of fabric by predetermined intervals. Thus, cushioning products may be maximally improved in bendability, and because only fabric is provided in spaces between the foams which are individually cut and attached to the upper surface of fabric, air may naturally flow through the protection pad, ultimately increasing air permeability of products.
However, this method is problematic because a large number of processes are required to uniformly attach (or adhere) the plurality of cross-linked foams to a predetermined portion of one surface of fabric, and thereby additional costs are incurred, and thus this method cannot be actually applied to general-purpose products. When these products are used for a long period of time in a state of being worn by a user or they are washed, the individual cross-linked foams attached to the surface of the fabric using the adhesive may be partially detached from the adhesion surface of the fabric, and thus they may be limitedly used only for products in which durability is ensured in a predetermined range.
Furthermore, because practical limitation factors are accompanied by the process of firmly attaching individually discrete cross-linked foams to the surface of fabric, the outer surface of the cushioning product formed by combining the plurality of cross-linked foams becomes typically planar. Thus, to make a cushioning product the outer surface of which is formed to have three-dimensional designs in various shapes, a plurality of individual cross-linked foams having a variety of three-dimensional shapes and dimensions is prepared and then attached to the surface of fabric using an adhesive. In this case, a plurality of molds is prepared so as to be adapted for individual foams having intended designs in three-dimensional shapes, as well as the complicated processes, after which individual foams are formed and then effectively attached to the upper surface of fabric. However, this case has many processing limitations and increased manufacturing costs, making it difficult to achieve the desired products.
Furthermore, in the conventional techniques, the cross-linked foams and the fabric are mainly bonded to each other using a sewing process or an adhesive. Particularly in the case of using an adhesive, a large number of processes should be conducted, including washing the adhesion surface, and applying a primer and an adhesive thereon, followed by performing drying and then compressing or heating the adhesive before compression, etc. Moreover, when a liquid adhesive is excessively used, it may penetrate into the fabric. The case where an adhesive is used in a minimum amount needs an industrial adhesive containing an organic solvent, as necessary, in order to ensure strong adhesion between the fabric and the cross-linked foam, undesirably causing many environmental problems.